This invention relates generally to magnetic resonance imaging (MRI), and more particularly the invention relates to MRI in which signal from fat is suppressed.
Refocused steady-state free precession (SSFP) experiments provide high SNR in relatively short scan times, but often suffer from extremely bright signal from fat. In many clinical applications of MR, bright fat signal can interfere with the desired signal (from water), making diagnosis more difficult.
Several techniques exist for fat suppression in non-refocused (xe2x80x9cspoiledxe2x80x9d) imaging experiments, but these methods are incompatible with refocused SSFP. Recently, a few techniques have been proposed that can suppress fat in refocused-SSFP sequences, but most require an increase in scan time, and can suffer from inconsistent or incomplete fat suppression. See, for example, Vasanawala et al. U.S. Pat. No. 6,307,368; Deimling U.S. Pat. No. 6,339,332; and Scheffler et al., Magn Reson Med, 45 (6); 1075-1080, 2001.
The present invention is directed to a method of generating image with fat-suppressed SSFP contrast without requiring any additional scan time over standard SSFP procedures and with comparable signal-to-noise ratio (SNR) to other techniques.
In accordance with the invention, oscillating steady-state free precession is employed to achieve fat suppression in MRI signals. The invention is particularly useful for fat suppressed images in areas of motion such as the heart, where rapid imaging is imperative in order to reduce motion-related signal artifacts. The method can be more robust than current techniques, making it an attractive alternative for clinical use in a variety of studies including cartilage imaging, abdominal imaging, and coronary artery imaging, for example.
Briefly, in an xe2x80x9coscillatingxe2x80x9d steady state sequence, a pattern of tips and precession is repeated every Ntips TRs in order to produce useful contrast. In one embodiment, a specific oscillating sequence has Ntips=4, but sequences with other repetition intervals that generate interesting contrast can be used. With a repetition interval of 4xc2x7TR, four distinct steady states are produced.
The invention and objections and features thereof will be more readily apparent from the following detailed description and dependent claims when taken with the drawings.